1) No, they do not cut off the light pattern.
2) Google it. Tons of automotive site carry them, or find your local mazda parts dealer, they can order them if not stock them.
3) Yeah matching color usually looks best, or just black, mine is sunburst yellow and ordered black ones tonight. But if you have an exterior paint theme, such as idk like, red effects on white body base, red would look better, or vise versa, white on red, white would look better.